SidewallerTire & wheel calculators

275/40R18 vs 235/50R18

235/50R18 is 2.2% taller (+0.59 in) and 1.57 in narrower than 275/40R18.

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Close match

235/50R18 is 2.2% taller than 275/40R18. That is inside the ±3% most shops treat as a straight swap.

275/40R18235/50R18Change
Diameter26.66″27.25″+0.59″+2.2%
Width10.83″9.25″−1.57″−14.5%
Sidewall4.33″4.63″+0.30″+6.8%
Circumference83.8″85.6″+1.9″+2.2%
Wheel18″18″Same
Revs per mile756740−16
SideTread
275/40R18235/50R18
Speedometer shows 60 mph61.3mph

Real speed on 235/50R18.

Ground clearance+0.30in

Change in height under the axle.

Width per side−0.79in

On the same wheel, split inboard and outboard.

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275/40R18 or 235/50R18?

Can I use 235/50R18 instead of 275/40R18?

235/50R18 is 2.2% taller than 275/40R18. That is inside the ±3% most shops treat as a straight swap. Also match or beat the original load index and speed rating, and check that the wheel width suits the new tire.

Will my speedometer be off?

At an indicated 60 mph on 235/50R18 you are really doing 61.3 mph if the speedometer was set up for 275/40R18. Going the other way, 275/40R18 would make it read 58.7 mph at a real 60.

How much ground clearance does it change?

Half the diameter difference: +0.30 in (+8 mm) under the axle.

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